Solvent refining of oil



Patented Dec. 27, 1938 UNITED. STATES PATENT OFFlCE SOLVENT REFINING OF OIL Waldersee B. Hendrey and Leon W. Cook, Beacon, N; Y., assignors to The Texas Company, New- York, N. Y., a corporation of Delaware No Drawing. Application April 2, 1937,

Serial No. 134,523

4 Claims.

acetic acid.

It has been found that a solvent comprising of trichloracetic acid provides an eflicient solvent for the extraction of residual lubricating oil fractions to produce therefrom lubricating oil products of high viscosity index and low residual carbon content. The presence of the chlorinated acetic acid improves the solvent refining action of the solvent particularly in the case of residual stocks. The presence of the acid results in obtaining a higher yield of refined oil having a lower 20 residual carbon content than is possible when using the solvent alone.

In this respect, the results are different from those obtained when the same amount of acid is added to certain other solvents, such as furfuryl acetate or methyl furoate for example. In the case of these latter solvents, the presence of chlorinated acetic acid results in no substantial improvement as regards the character of the refined oil. I

Thus, when extracting a dewaxed parafiin residuum, such as will be described later in more detail, with furfuryl acetate containing by weight of trichloracetic acid, the characteristics of the resulting refined or rafiinate oil are sub- 35 stantially unchanged from those of the oil obtained when extracting with the furfuryl acetate alone. Also in the case of methyl furoate containing a small amount of acid, the resulting yield of rafiinate oil was reduced considerably while 40 the residual carbon content of the oil remained about the same as when the methyl furoate contained noacid.

In contrast with the above when extracting with tetrahydrofurfuryl acetate containing a small amount of acid, the yield of raffinate oil is improved and in addition, the residual carbon content of the oil is reduced. This improvement is illustrated by the following example in which a dewaxed parafiin residuum having the following characteristics was extracted:

Gravity A. P. I 1'7. 8 Saybolt Universal viscosity 210 F 159 Viscosity index 56 Viscosity gravity constant 876 55 Carbon residue per cent 6.9

tetrahydrofurfuryl acetate and a small amount.

Samples of the foregoing oil were extracted with (a) tetrahydrofurfuryl aceate alone andlb) tetrahydrofurfuryl acetate containing 10% by Weight of trichloracetic acid. In each case, the

oil was subjected to extraction using two parts of solvent to one part of oil. Separation into extract and rafiinate phases occurs. The extract phase comprised heavy low viscosity index constituents of the oil dissolved in the bulk of the solvent while the raffinate phase comprised high viscosity index oil mixed with a small amount of the solvent.

The phases were separated from each other and the solvent removed therefrom. The tests on the raflinate and extract oil after removal of the solvent in each case were as follows:

From the foregoing, it will be observed that the rafiinate obtained when extracting with tetrahydrofurfuryl acetate containing a small amount of acid amounted to 88.5% of the charge and had a residual carbon content of 5.3%. Where no acid was used, the raffinate amounted to 82.5% and had a residual carbon content of 6.3%.

' It is contemplated that the solvent dosage and the extraction temperature may vary from that specifically mentioned above in describing the specific examples. It is also contemplated that instead of trichloracetic acid other acidic modifying solvents may be used, such as chloracetic acid, dichloracetic acid, and the corresponding fluorine, bromine and iodine derivatives. The amount of such acid used will be around 5 to 20% by volume of the extraction solvent.

Moreover, it may be advantageous in many cases to dilute the lubricating oil stock with a suitable diluent solvent prior to efiecting extraction with the selective solvent. A suitable diluent may comprise a liquefied normally gaseous petroleum hydrocarbon, such as propane.

Obviously, many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and which comprises extracting the 'oil with tetrahydrofurfuryl acetate in the presence of around.

5 to 20% of halogenated acetic acid such that upon separation of the oil and solvent into extract. and rafiinate phases the'raffinate phase will contain a larger proportion of high viscosity index oil than when the extraction ismade in the absence of the acid, forming an extract phase containing low viscosity index'constituents dissolved in the bulk of the solvent anda raffinate phase comprising high viscosity index constituents mixed with a small amount of the solvent, separating the two phases and removing'the solvent therefrom.

2. The method of refining oil by solvent extraction to separate it into fractions respectively rich in low and high viscosity index constituents which comprises extracting the oil with tetra hydrofurfuryl acetate in the presence of a small amount of a halogenated acetic acid, forming an extract phase containing low viscosity index constituents dissolved in the bulk of the solvent and a raffinate phase comprising high Viscosity index constituents mixed with a small amount of solvent, and separating the two phases. 7

3. .The method of refining oil by solventv extraction to separate it into fractions respectively rich in low and high viscosity index constituents which comprises extracting the oil with tetrahydrofurfuryl acetate in the presence of a small amount of trichloracetic acid, forming an extract phase containing low viscosity index constituents dissolved in the bulk of the solventand a raffinate phase comprising high viscosity index constituents mixed with a small amount of solvent, and

separating the two phases.

4. The method of refining residual lubricating oil containing residual carbon-forming bodies in substantial amount by solvent extraction so as i to separate the oil into fractions respectively rich in low and high viscosity index constituents which comprises mixing the residuum with a solvent comprising tetrahydrofurfuryl acetate and containing a substantial amount of halogenated raflinate phasecomprising high viscosity index constituents mixed with a small. amount of solvent, and separating the two phases.

WALDERSEE B. HENDREY.

LEON W. COOK. a 

